A substrate processing system is used for fabricating semiconductor devices including flat panel displays (FPDs). The substrate processing system has processing modules and a substrate carrying mechanism for carrying a substrate from and to the processing modules. The substrate carrying mechanism of the substrate processing system delivers substrates sequentially to the processing modules. The processing modules process the substrates by predetermined processes, respectively. It is possible that the entire surface of the substrate cannot be uniformly processed unless the substrate is positioned correctly at a predetermined position in each processing module. Although the substrate carrying mechanism is constructed so as to exhibit high carrying accuracy, a positioning operation is essential to accurately positioning the substrate.
A substrate holder positioning method disclosed in, for example, Patent document 1 or 2 carries a positioning device provided with a detector, such as a camera or an image sensor, by the substrate holder, determines a distance of the substrate holder from a predetermined reference position on the basis of the position of the substrate holder determined by the detector, and then executes a correcting operation, namely, a teaching operation, for correcting the dislocation of the substrate holder from the reference position.